A Subsurface Taj Mahal: Seismic Geomorphology Calibrated with Core and Log Data Provides Key Building Blocks for Modeling Tidally-Influenced Estuarine Deposits in the Gulf of Cambay, Western India
Lesli J. Wood, Satyashis Sanyal, Nikhilesh Dwivedi, Stuart Burley, 2010. "A Subsurface Taj Mahal: Seismic Geomorphology Calibrated with Core and Log Data Provides Key Building Blocks for Modeling Tidally-Influenced Estuarine Deposits in the Gulf of Cambay, Western India", Seismic Imaging of Depositional and Geomorphic Systems, Lesli J. Wood, Toni T. Simo, Norman C. Rosen
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The present day Gulf of Cambay contains several prolific oil and gas fields in paleo-Cambay estuarine deposits. As these fields mature, there is a need for an improved understanding of their geological framework to enable secondary recovery methods to be employed to optimise recovery. Although traditional seismic interpretation is suitable for structural analysis, a more integrated approach employing multiple tools is necessary if an accurate understanding of these stratigraphically complex depositional systems is to be achieved. A geocellular model using Petrel software has been constructed for the Miocene oil reservoirs of the Lakshmi Field, Gulf of Cambay, integrating quantitative seismic geomorphologic interval analysis with well log facies interpretation, depositional and petrophysical facies from core, and observed production relationships between the eleven wells available in the field.
Studies of the modern environments in the Gulf of Cambay, analog studies of outcrop and other modern systems, and direct seismic morphologic and log analysis of the intervals of interest provided a depositional framework for populating the static stratigraphic model with seven facies. Log correlation panels based on regional flooding surfaces and mapped sequence boundaries were integrated with seismic horizon mapping and seismic geomorphologic interpretations to produce a multi-meter thickness grid of zones for Petrel modeling. The framework was constrained by engineering data and the interpreted connectivity relationships between sands.
Results of this work demonstrate that the Miocene stratigraphy in the Lakshmi Field comprises two large erosion and valley-fill cycles, with the lowermost estuarine fill comprising three parasequence sets. Each parasequences contains tidal bar, tidal channel, estuarine distributary channel, tidal flat and mud flat depositional elements. In more proximal areas, bay head delta elements are thought to be developed. The tidal flat elements show the development of two sub-elements; tidal flat channels and associated crevasse splays. Since structural closures parallel depositional dip, it is important to recognize the elements (depoforms) and their spatial relationship to post-depositional trap orientation.